1. Field of the Invention
This invention relates to a method of processing a light-sensitive material by bringing a peeling means into close contact with the material in place of effecting washing off of the light-sensitive layer (for example, a silver halide emulsion layer or a non-silver salt light-sensitive layer) of the light-sensitive materials. Particularly, it relates to a processing method preferably employed for making an aluminum lithographic printing plate utilizing a silver complex diffusion transfer process which uses an anodized aluminum plate as a support.
2. Prior Art
With regard to a lithographic printing plate using a silver complex diffusion transfer process (the DTR method), some examples are described on pages 101 to 130 of André Rott and.
Edith Weyde, “Photographic Silver Halide Diffusion Processes”, published by the Focal Press, London and New York (1972).
As described therein, there have been known two kinds of lithographic printing plates using the DTR process, i.e., a two sheet type in which a transfer material and an image-receiving material are separated and a mono-sheet type in which these materials are provided on one support. The two sheet type lithographic printing plate is described in detail in Japanese Provisional Patent Publication No. 158844/1982. Also, the mono-sheet type is described in detail in U.S. Pat. No. 3,728,114.
The mono-sheet type lithographic printing plate utilizing the silver complex diffusion transfer process with the use of an aluminum plate as a support (hereinafter referred to as “an aluminum lithographic printing plate”) is described in detail in Japanese Provisional Patent Publications No. 118244/1982, No. 158844/1982, No. 260491/1988, No. 116151/1991 and No. 282295/1992, and U.S. Pat. No. 4,567,131 and No. 5,427,889.
In the above-mentioned aluminum lithographic printing plate, physical development nuclei are carried on a roughened and anodized aluminum support, and a silver halide emulsion layer is further provided thereon. A general process for making this lithographic printing plate comprises the steps of exposure, DTR development processing, water washing processing (washing off: removal of a silver halide emulsion layer with washing solution) and finishing processing.
More specifically, a metal silver image portion is formed on the physical development nuclei by the development processing and the silver halide emulsion layer is removed by the subsequent washing processing to expose the metal silver image portion (hereinafter referred to as a “silver image portion”). Simultaneously, the anodized aluminum surface itself is exposed as a non-image portion.
After the washing processing, a finishing solution containing a protective colloid such as gum arabic, dextrin, carboxymethyl cellulose, polystyrenesulfonic acid, etc. is coated on the exposed silver image portion and the non-image portion for protecting the same. A processing of the so-called gum coating is applied to the surface of the plate. The finishing solution is also called as a fixing solution and it is general that it contains a compound which makes the silver image portion oleophilic such as a nitrogen-containing heterocyclic compound having a mercapto group or a thione group (hereinafter referred to as an “oleophilic agent”).
The above-mentioned aluminum lithographic printing plate has a merit that a printing plate excellent in printing endurance can be easily obtained as compared with a lithographic printing plate in which a subbing layer, a silver halide emulsion layer and a physical development nuclei layer are provided in this order on a flexible support such as a film or a polyethylene-coated paper, etc., but it involves various kinds of problems.
On of the problems is that the silver halide emulsion layer, etc. are removed by a washing solution so that it is necessary to treat and dispose a large amount of a washing solution containing gelatin or silver, etc. which becomes one of the serious environmental or economical problems.
To solve the above-mentioned problems, there are proposed to peel off an emulsion layer by bringing a peeling sheet into close contact with the emulsion layer to peel off the emulsion layer in U.S. Pat. No. 5,068,165 and No. 5,213,943, and Japanese Provisional Patent Publication No. 318553/1992. More specifically, peeling sheets comprising a substrate and a gelatin layer or a cured gelatin layer containing a matte agent coated on the substrate are shown. However, the peeling sheets in the specific examples have defects that they not only require a long contacting time until peeling off thereof.
Another problem is that an amount of waste liquor of the developing solution is large. That is, a developing solution containing a developing agent such as hydroquinone, etc. has been used for making an aluminum lithographic printing plate. In this developing solution, a relatively large amount of the developing solution must be replenished compulsorily so that an excessive developing solution overflowed is exhausted and disposed. Thus, an amount of the developing solution to be used for developing the aluminum lithographic printing plate per unit area becomes large as compared with the lithographic printing plate using a flexible support. And yet, when a developing solution is used for a predetermined running processing time, the used developing solution must be changed to a new developing solution. Thus, there are environmental and economical problems since such a large amount of the developing solution must be disposed of as a waste solution.
A further problem is that an aluminum oxide layer of an anodized aluminum support is dissolved by an action of a high pH developing solution, so that changes in developing conditions affect to formation of DTR development silver so that a lithographic printing plate having good printing properties cannot be made stably.
On the other hand, a light-sensitive material comprising a light-sensitive composition containing no silver salt has been known. This light-sensitive composition causes chemical change of a molecular structure by photoreaction (irradiation of UV rays or visible rays), and as a result, changes are caused in physical phenomenon (physical properties). As a chemical change due to an action of light, there are cross-linking, polymerization, decomposition, decomposition polymerization, functional group-modification, etc., and also there are various factors such as solubility, adhesiveness, refractive index, substance permeability and phase change, etc. Such a light-sensitive composition has practically been used in a broad field such as a printing plate, resist, paint, coating agent, color filter, etc. Moreover, it has been used in the field of photoresist using a photographic plate-making technology (photolithography) and developed. The photoresist is to utilize change in solubility due to the photoreaction.
As an example in which a light-sensitive material comprising the above-mentioned photosensitive composition is applied to a lithographic printing plate, it has been generally known a PS plate (which is an abbreviation of “Presensitized Plate”) in which a light-sensitive resin layer is provided on an aluminum support. In the PS plate, there are two types of a negative type and positive type materials. The negative type material is to cure an exposed portion and remove an unexposed portion by dissolving the portion using a developing solution whereby a cured film (exposed portion) is formed on the aluminum support with a shape depending on an exposure pattern. The positive type material is contrary to the above, to solve an exposed portion by a developing solution whereby a film (unexposed portion) is formed on the aluminum support depending on an exposure pattern.
As materials for making the PS plates as mentioned above, there are described in detail, for example, in “Outline of PS plate”, written by Teruhiko Yonezawa (published by Insatsu Gakkai Shuppannbu, Japan), “Light-sensitive polymer”, written by Gentaro Nagamatsu and Hideo Inui (published by Kodansha, Japan) or “Photopolymer Technology” written by Tsuguo Yamaoka and Gentaro Nagamatsu (published by Nikkan Kogyo, Japan).
Also, in addition to the above-mentioned PS plate, there is a lithographic printing plate to be used in a CTP (Computer To Plate) system. The CTP system is a system in which original data converted into digital information are directly subjected to image exposure to a printing plate by using a laser beam. As a light source, helium-neon laser, argon laser, near infrared semiconductor laser, YAG laser, etc., have been frequently utilized.
As a printing plate for CTP as mentioned above, a printing plate which is capable of effecting laser beam exposure utilizing a photopolymerization reaction containing a polymerizable monomer has been known. It has been explained in, for example, written by Shigeki Shimizu, “Insatsu Zasshi”, vol. 78, p. 9, 1995, etc. Also, in Japanese Patent Publication No. 105353/1994 or Japanese Provisional Patent Publication No. 230594/1997, an example of a photopolymerizable composition comprising a polymer into which a polymerizable unsaturated bonding group having a specific structure is introduced at a side chain, a photopolymerization initiator and a compound having at least one of an ethylenically unsaturated bond.
As examples of light-sensitive compositions for forming a negative type image by utilizing a laser beam, there may be mentioned, for example, in Japanese Provisional Patent Publications No. 90885/1998, No. 127694/1997 and No. 138500/1997, etc., and as for the use particularly of a lithographic printing plate, thee may be mentioned those described in Japanese Provisional Patent Publications No. 20629/1997, No. 271029/1995, No. 244226/1997, No. 212252/1999 and No. 231535/1999, etc. Of these, lithographic printing plates having a light-sensitive layer basically containing a phenol resin, a light Absorbent and an acid generator. Such a lithographic printing plate is, for example, subjected to exposure with a high output laser, etc., so that solubility of the phenol resin to a developing solution changed by an acid generated from the acid generator due to change in cross-linking density, etc., is utilized.
The light-sensitive material comprising the above-mentioned light-sensitive composition involves a problem that components of a developing solution change with a lapse of time since a not-cured light-sensitive layer is dissolved in the developing solution and removed, so that much amount of a replenishing solution for the developing solution is required whereby an amount of a waste solution becomes large.